Hi, I have ordered some switching power supplies from china (originally supposed to supply LED strips) and I want to make a power supply from them, but I measured that the ground of the 12v output of the supply has a voltage about 90v referentially to The Ground (meant the ground which the most of oscilloscopes is grounded to) but when shorted with The Ground ,only few hundreds of miliamperes flows (I think it was about 300mA at most). And I have also watched Dave's video called "How to not blow up oscilloscope". There he said that the measured circuit should be isolated from the scope otherwise the scope may blow up
![Broken! :-BROKE](https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif.pagespeed.ce.z9RuKVWKjY.gif)
, when falsely connected. So I have a question, is it safe to measure circuit connected to the power supply I am gonna make by oscilloscope when attaching the ground aligator clip to the ground of the supply having 90v to The Ground?
Thanks a lot (I would like to not blow up my new scope immediately
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
)
![Broken! :-BROKE](https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif.pagespeed.ce.z9RuKVWKjY.gif)